Ever been any natural extinctions:Was Selective preservation of species

[Patrick Foley]

To those still extant,

Extinctions occur during much of the Phanerozoic (last 600 MY) at rates like once
per species per million years or more. G G Simpson estimated this for mammals
years ago, and Lawton, May and Stork recently reviewed the data for all manner of
organisms. Plant and shelly invertebrates can expect to live 1 to 10 times
longer. But this is from the fossil record. Note that the hominids fit this
fairly well. Lucy to Homo sapeins took about 4 species extinctions and about 4
MY.

Modern species are vanishing at a much faster rate (again reviewed in the book
Extinction Rates edited by Lawton and May 1995). perhaps 100 to 1000 times faster
than the usual. To see how to predict extinction times in local populations of
butterflies, check out Foley, P. 1994. Predicting extinction times from
environmental stochasticity and carrying capacity. Conservation Biology
8:124-137, where Euphydryas editha bayensis populations under Paul Ehrlich
appeared and in fact were doomed.

Patrick Foley
patfoley at csus.edu

Extinction is natural, but contemporary rates are only natural in a very
perverted way.

Patrick Foley
patfoley at csus.edu

Neil Jones wrote:

> On Saturday 27 April 2002 08:42 pm, Martin Bailey wrote:
> > Norbert,
> >
> > I deleted inadvertently your last post with copy to leplist.  If my memory
> > serves me correctly, the question that you posed was should we try to stop
> > a species from disappearing if it appears to be at the end of its
> > evolutionary life?
>
> I think there is a red herring implicit in this argument. The real  question
> is are there any known examples of Lepidopteran extinctions. that were _not_
> caused by man-made factors?
>
> It is frequently cited that extinction is a natural process. (This is usually
> done by the opponents of conservation.) However, in reality surely the level
> of natural extinctions is utterly minuscule when compared to those which are
> "man-made".
>
> I am very aware that local population extinctions are a natural phenomenon
> and indeed very much a  part of the study of population dynamics but
> extinction of taxa by natural means is a phenomenon that has to be measured
> over the geological timescale.
>
> --
> Neil Jones- Neil at nwjones.demon.co.uk http://www.butterflyguy.com/
> NOTE NEW WEB ADDRESS
> "At some point I had to stand up and be counted. Who speaks for the
> butterflies?" Andrew Lees - The quotation on his memorial at Crymlyn Bog
> National Nature Reserve
>
>
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